Sten – Värmland

We are two blocks of kyanite quartzite from Hålsjöberget northeast of Torsby in Värmland. Kyanite quartzite is Värmland's landscape stone, but it is not the case that all of Värmland consists of kyanite quartzite or that it is even a particularly common rock there. No, kyanite quartzite is a very unusual, almost unique rock type, which is only found at Hålsjöberget.

The geologists have also disagreed a lot about how the kyanite quartzite was formed. Quartzite is a rock that consists almost exclusively of the mineral quartz. Most often, the quartzite has been formed from quartz sandstone. Most of the sand grains in a sandstone consist of quartz, and if such a quartz sandstone is buried at a great depth, the quartz recrystallizes, so that it forms a dense, coherent mass of quartz that becomes very hard, a quartzite. But kyanite quartzite also contains some of the bluish mineral kyanite, that's what makes it so beautiful and attractive, although the blue kyanite may not be so clearly visible in the two of us, at least not to the naked eye. Kyanite is an aluminum-containing mineral that forms at high pressure deep in the earth's crust. So it is possible that the kyanite quartzite formed from an impure sandstone, which also contained a lot of clay, which in turn is rich in aluminum. If the clay-rich sandstone was pressed deep into the earth's crust and subjected to high pressure, it is possible that it was converted to kyanite quartzite.

But some geologists believe that warm water solutions were instead involved to transform the rock into kyanite quartzite. Maybe in that case it started with a quartz-rich rock of volcanic origin instead, and not some sandstone. Then hot water solutions leached various elements out of the rock, leaving only silicon and aluminum, plus oxygen, which is also found in quartz and kyanite. And then the pressure caused the rock to transform into kyanite quartzite.

Which is more correct, if anything, we are not going to talk more about, we hardly remember ourselves how we formed. Since it is so uncertain how we were formed, it is also uncertain how old we are. It also depends on whether by that you mean the age of the original rock (be it sandstone or a volcanic rock), or the time when we were transformed and became kyanite quartzite. But most of the bedrock in this part of Värmland is between 1500 and 1700 million years old, so our age should be somewhere within this time interval, at least the age of the original rock.

We said that many people think that kyanite quartzite is a very beautiful rock, white with hints of blue. It is also very hard and durable. Therefore, it has been quarried from time to time at Hålsjöberget and sawed and polished into very durable worktops. A kitchen worktop made of kyanite quartzite certainly will impress your neighbours!

Geologist Åke Johansson
Swedish Museum of Natural History